Question

Chronic drug administration can result in which of the following effects? Explain the answer.

            a. down regulation of the receptor

            b. receptor desensitization

            c. tachyphylaxis

            d. drug tolerance

Answer 1

All of these effects can happen as a consequence of chronic drug administration. But here, the answer can be selected as option a. Downregulation of the receptor.

​​​​​​   When there is chronic drug administration, the receptors are continuously exposed to an excessive amount of the drug. This will lead to decreased synthesis of new receptors leading to reduction in the number of receptors. This is called as downregulation of receptors.

Downregulation of receptors can lead to it's desensitization or internalization.

Downregulation and desensitization of receptors can lead to tachyphylaxis. It is also called as acute drug desensitization. It is an acute or sudden reduction in response to a drug. Here, the desensitization is occurring very rapidly. That means there is a rapid reduction in the drug response to the repeated doses over a short time period.

Drug tolerance means loss of response to a drug, which is occuring more gradually. That means more high doses will be required to produce the desired effect.

So we can conclude like this: chronic drug administration ----- Downregulation of receptors ------ Receptor desensitization ------ Tachyphylaxis ------ Drug tolerance